同位素在饮马河流域示踪地下水的应用

本文阐述了环境同位素在地下水研究中的作用和饮马河流域水文地质概况。运用稳定同位素D和~(18)O千分偏差值分析了地下水成因、地表水与地下水的补排关系。采用放射性同位素~3H、~(14)C和地下水动力学等方法计算了地下水年龄。通过分析和讨论,对地下水成因和地下水循环周期有了新认识。因此利用环境同位素示踪地下水,对选择供水水源地具有重要意义。     

322矿田花岗岩与铀矿床的同位素研究

本文应用同位素地质方法研究322矿田内花岗岩的年龄和成因、成矿热液和成矿物质来源等问题。研究表明,矿田内的成矿母岩为改造型花岗岩,其Rb-Sr同位素年龄为198.8Ma,成矿热液来自花岗岩结晶矿物颗粒间和裂隙中的溶液以及大气降水。成矿物质主要来自花岗岩,部分也来自岩体周围的寒武系地层。     

湖泊沉积物中有机碳稳定同位素测定及其古气候环境意义

１９９１年５月，利用澳大利亚转动式采样器在江苏固城湖获得总长６．２ｍ的完整柱状岩芯，以５ｃｍ间隔采样，对样品中有机质的稳定碳同位素研究表明。     

四川稻城地区温泉流体地球化学特征及地震活动性分析

稻城地区位于青藏高原东南缘的川滇地块北部,为揭示该区域温泉流体地球化学特征以及其和地震活动性之间的关系,本次研究采集了稻城地区6个温泉的水样以及逸出气体样品。对温泉水中离子组分和浓度,温泉逸出气体组分及气体同位素进行了测试,得到以下认识。研究区温泉水化学类型主要为HCO₃-Na和HCO₃-Na·Ca型,通过阳离子温标估算热储温度在74℃～159℃之间,循环深度在2.2 km～5.0 km之间。温泉气体中CO₂主要是由储层中的碳酸盐岩受热分解或溶解产生的,氦来自幔源组分的比例较低,在0.4%～2.4%之间,研究区的温泉是由沿断裂带渗入的大气降水经地壳深部的热源加热形成的。在稻城地区,循环深度以及幔源气体贡献率等不同的温泉流体地球化学特征与地震活动性之间有很好的对应关系,并且研究区地震活动性要弱于周缘鲜水河断裂地区等深部流体上涌地区。同时在区域尺度上,未来位于断裂交汇部位的稻城仲堆温泉一带的地震活动性最值得关注。     

Bioaccumulation and enantiomeric profiling of organochlorine pesticides and persistent organic pollutants in the killer whale (Orcinus orca) from British and Irish waters

Concentrations and enantiomeric profiles for a range of organochlorine compounds are reported in blubber samples from a number of individual killer whales (Orcinus orca) from British and Irish waters. Elevated contaminant levels and enriched isotopic ratios were determined in one individual whale sampled in the Scottish Western Isles compared to the others suggesting marine mammal based dietary influences. The potential application of isotopic ratios to model contaminant uptake, enantioselective enrichment and accumulation is demonstrated. Data are presented which provide information on enantioselective enrichment factors (EFs) for o,p'-DDT, alpha-HCH and toxaphene congeners CHB26 and CHB 50. This dataset further improves the current database on reported levels of a number of contaminants and provides additional background information on potential metabolic processes in killer whales from British and Irish waters.     

The last interglacial sea-level high stand on the southern Cape coastline of South Africa

The continental margin of southern South Africa exhibits an array of emergent marginal marine sediments permitting the reconstruction of long-term eustatic sea-level changes. We report a suite of optical luminescence ages and supplementary amino acid racemization data, which provide paleosea-level index points for three sites on this coastline. Deposits in the Swartvlei and Groot Brak estuaries display tidal inlet facies overlain by shoreface or eolian facies. Contemporary facies relations suggest a probable high stand 6.0-8.5 m above modern sea level (amsl). At Cape Agulhas, evidence of a past sea-level high stand comprises a gravel beach (ca. 3.8 m amsl) and an overlying sandy shoreface facies (up to 7.5 m amsl). OSL ages between 138 ± 7 ka and 118 ± 7 ka confirm a last interglacial age for all marginal marine facies. The high stand was followed by a sea-level regression that was associated with the accumulation of eolian dunes dating to between 122 ± 7 ka and 113 ± 6 ka. These data provide the first rigorous numerical age constraints for last interglacial sea-level fluctuations in this region, revealing the timing and elevation of the last interglacial high stand to broadly mirror a number of other far-field locations.     

Measurements of the18O/16O ratio of dissolved oxygen in the North Sea during FLEX 76

In spring 1976 a special part of the North Sea was the subject of research by a group of international scientists in the so-called Fladenground Experiment 1976 (FLEX 76). Our team participated aboard the research shipPlanet in an attempt to study the oxygen exchange between sea and atmosphere and the mixing within the water column. The water samples were taken in a small area during a period of two weeks. The water depth did not exceed 140 m. The dissolved oxygen was extracted using a vacuum system, and stored after adsorption on a molecular sieve. In the laboratory the oxygen was burned to carbon dioxide and the¹⁸O/¹⁶O ratio was determined with a mass spectrometer. At the surface the sea water was saturated with air and showed the¹⁸O/¹⁶O ratio of atmospheric oxygen. Towards the deeper layers the oxygen was consumed, and as a result the heavier isotope¹⁸O was enriched. This enrichment can be seen in a very marked manner even in the upper 100 m of the sea. In our case the¹⁸O enrichment indicates that the mixing processes did not exchange the oxygen of the layers beneath the surface rapidly.     

Isotope geochemistry of the Tieluping silver-lead deposit, Henan, China: A case study of orogenic silver-dominated deposits and related tectonic setting

The Tieluping silver deposit, which is sited along NE-trending faults within the high-grade metamorphic basement of the Xionger Terrane in the Qinling orogenic belt, is part of an important, recently discovered Mesozoic orogenic-type Ag-Pb belt. Ore formation includes three stages: an early barren quartz-pyrite stage (E), an intermediate polymetallic sulfide ore stage (M), and a late barren carbonate stage (L). Carbon, sulfur and lead isotope systematics indicate that the E-stage fluids are deeply sourced; the L-stage fluids are shallow-sourced meteoric water; whereas the M-stage fluids are a mix of deep-sourced and shallow-sourced fluids. Sulfur and lead isotope data show that the ore-forming fluids must have originated from a source with elevated radiogenic lead and low ³⁴S values, that differs significantly from exposed geologic units in the Xionger Terrane, the lower crust and the mantle. This supports the view that the carbonate-shale-chert sequences of the Guandaokou and Luanchuan Groups south of the Machaoying fault might be the favorable sources, although little is known about their isotopic compositions. A tectonic model that combines collisional orogeny, metallogeny and hydrothermal fluid flow is proposed to explain the formation of the Tieluping silver deposit. During the Mesozoic collision between the North China Craton and South China Block (Early-Mid Triassic Indosinian Orogeny), crustal slabs containing the carbonate-shale-chert sequences of the Guandaokou and Luanchuan Groups, locally rich in organic matter (carbonaceous shale), were thrust northwards beneath the Xionger Terrane along the Machaoying fault. Metamorphic devolatilisation of this underthrust slab probably provided the ore-forming fluids to develop the Ag-Pb ore belt, which includes the Tieluping silver deposit. Fluids and magmas were emplaced during extensional stages related to the Jurassic-Cretaceous Yanshanian Orogeny.Editorial Handling: B. Lehmann     

Neoproterozoic to Early-Palaeozoic magmatic evolution in the Gondwana-derived Austroalpine basement to the south of the Tauern Window (Eastern Alps)

In the Austroalpine Basement to the south of the Tauern Window, distinct suites of metabasites occur with orthogneisses in pre-Early-Ordovician units. Tholeiitic and alkaline within-plate basalt-type metabasites are associated with acid meta-porphyroids in the post-Early-Ordovician Thurntaler Phyllite Group. According to their correlated trace element abundances, metabasite zircons crystallized with their host rocks. Protolith Pb–Pb zircon ages, whole-rock Ta/Yb–Th/Yb and oxygen, Sr, Nd isotope data define two principal evolution lines. An older evolution at elevated Th/Yb typical of subduction-related magmatism, started by 590-Ma N-MORB-type and 550–530 Ma volcanic arc basalt type basic suites, which mainly involved depleted mantle sources. It finished with mainly crustal-source 470–450-Ma acid magmatites. An other evolution line by tholeiitic and 430-Ma alkaline within-plate basalt-type suites in both pre- and post-Early-Ordovician units is characterized by an intraplate mantle metasomatism and enrichment trend along multicomponent sources. These magmatic evolution lines can be related to a plate tectonic scenario that involved terranes in a progressively mature Neoproterozoic to Ordovician active margin, and a subsequent Palaeo-Tethys passive margin along the north Gondwanan periphery.